地下水中の溶存ガス分析法の開発 [in Japanese] Improvement of analytical method for dissolved gases in natural waters [in Japanese]
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For the purpose of geochemical earthquake prediction, an analytical method for dissolved gases in natural waters was improved and its validity was examined. The method is based on the dissolution equilibrium between gas phase and sample water in a vessel. Size and shape of glasswares, materials suitable for collecting micro- bubbles, duration to attain gas exchange equilibrium, and other analytical conditions were experimentally examined. Two lines of procedures were compared. (1) Bubble-trap type, where micro-size bubbles separated from groundwater owing to a pressure drop on the earth surface are collected, and (2) water-sprinkle type, where groundwater is sprinkled over an air in a glass flask through numerous pinholes, and the air tends to be at equilibrium with the dissolved gases owing to gas exchange. Compositions of the gas phase are determined by a gas chromatography. Both analytical procedures are simple enough to be applicable to continuous monitoring of variation of dissolved gases in natural waters. Preliminary observations for several days with the two procedures at an artesian well, 1600m deep, in the vicinity of Nagoya showed that the water-sprinkle type is better for a long-term monitoring, although it failed to disclose an obvious cyclic variation of gas composition associated with the earth tide.
Chikyukagaku 23(1), 53-60, 1989
The Geochemical Society of Japan